1. Field of the Invention
The present invention relates to an apparatus for reading a radio frequency identification (RFID) tag information configured to read information from an RFID tag capable of radio communication of information with the outside and an RFID tag information reading system.
2. Description of the Related Art
A Radio Frequency Identification system configured to read or write information with respect to a small-sized RFID tag is known. In this RFID system, a reader/writer transmits an inquiry and receives a response in a non-contact manner with respect to the RFID tag.
In a label-shaped RFID tag, for example, an RFID tag circuit element is disposed. The RFID tag circuit element is provided with an IC circuit part storing predetermined RFID tag information and an antenna connected to the IC circuit part for information transmission and reception. If a transmission antenna of the reader/writer transmits a transmission wave to the RFID tag, the RFID tag circuit element replies in response to the transmission wave. In a prior art reference, for example, a method of smoothly conducting communication with the RFID tag circuit element in such an apparatus for reading RFID tag information configured to conduct communication is described.
In the prior art reference, a tag reader as an apparatus for reading RFID tag information configured to read information sent from an RFID IC tag, which is an RFID tag circuit element, that is, to read tag data is disposed. To this apparatus for reading RFID tag information, a speed detecting device as movement detecting portion configured to detect a moving speed of the apparatus for reading RFID tag information, that is, a moving speed of an automobile on which the apparatus is mounted is connected. According to the moving speed detected by the movement detecting portion, a direction variable device sets a direction of directivity of the apparatus for reading RFID tag information. As a result, accuracy of information reading from the RFID tag circuit element while the apparatus for reading RFID tag information is moving is improved.
In the meantime, a method in which when a response is prompted from a plurality of RFID tag circuit elements present in a communication range, time sections for reception divided into plural, that is, identification slots are prepared in advance has been already known. In this method, a response signal from each of the plurality of RFID tag circuit elements is temporally separated to the identification slots corresponding to tag identification information, for example, and detected.
By using such identification slots, occurrence of collision of the response signals from the RFID tag circuit elements is prevented, and accuracy of information transmission and reception can be effectively improved. However, since signals need to be received for the plurality of identification slots for a single reading command, time required for transmission and reception processing for a single command is inevitably prolonged. In the case of communication with the plurality of RFID tag circuit elements while moving as with the apparatus for reading RFID tag information of the prior art reference, communication areas are constantly changing. As a result, the reading command does not reach a part of the RFID tag circuit elements and causes no response. That is, there is a fear that non-started tag might remain. Also, though the command reaches and the RFID tag circuit element makes a response, the reading apparatus goes far away and cannot receive the response, that is, there is a fear that the reader does not receive a response. As described above, in the prior art reference, there is a possibility of two non-reading cases, namely, remaining of the non-started tag and non-reception of a response by the reader.
In the prior art reference, no particular consideration has been given to occurrence of non-reading caused by the identification slots as above and a measure against it in communication by the apparatus for reading RFID tag information while moving.